Hydraulic automatic selective transmission, including tilt plates



Jan. 29, 1952 HYDRAULIC AUTOMATIC SELECTIVE TRANSMISSION INCLUDING TILT PLATES Filed Feb.

G. P. LAY

5 Sheets-Sheet l Inventar Giles P. Lay

By Qa WWW EMM,

G. P. LAY

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Jan. 29, 1952 HYDRAULIC AUTOMATIC SELECTIVE TRANSMISSION, INCLUDING TILT PLATES Filed Feb. l, 1950 5 Sheets-Sheet 5 9.9 fgoo Giles P. Lay

IN VENTOR.

s Auoruy:

Jan. 29, 1952 G. P. LAY

HYDRAULIC AUTOMATIC SELECTIVE TRANSMISSION, INCLUDING TILT 'PLATES Filed Feb. l, 1950 5 Sheets-Sheet 4 *-/4/ lao/98 20 Fig. /0

Inventor GilesV P. Lay

y Qmmh Janf 29, 1952 G. P AY 2,583,656

HYDRAULIC AUTOMA'IC SELECTIVE TRANSMISSION, INCLUDING TILT PLATES Filed Fem 1,. 195o 5 sheets-sheet 5 g 26 F' /4 l /60 9 3 'f -F/oa 5 Inventor Patented Jan. 29, 1952 UNITED HYDRAULIC 'AUTOMATIC SELECTIVE TRANSMISSION, INCLUDING 'TILT )PLATES "Giles .P. Lay, Ontario, Oreg., .assigner yto La y Corporation, Portland, Oreg., Va .corporation of Oregon Application February 1, 1950,'SerialNo. 141,684

(CLM-687) Claims.

This is v.a continuation-in-part Aormy copending application, Serial No..25,;l73, which wasiiiled on May: 5,1 948,1no'wabandon'cd.

.An-iobject-of this invention'is to selectively control the lzactuati'on of a :power take-'o'if or driven shaft by correlating a fluid-:actuated transmission and a direct 'drive 'transmission of force applied toa drive shaft.

AImther-.objectlof 'this invention is to selectively control the power vtransferof "the fluid-actuated portion of .the-deviby manual and/or 'speedresponsive means.

.Another object fof this invention is to apply torque 'to a `drive shaft, 'transmit the same selectively to a counter shaftfanda driven shaft, the torque-applied to -`the dri-vensha'ft varying'from a'value of zero yto'maximum in accordance with the amount o'f `torque utilized by the counter shaft.

-Another object o'f 'this invention is to supply a lirstand second pumphaving the inlet Yof one connected with the 4outlet "o f another and the outlet of the said second pump being connected to the inlet of the'rst pump, thereby forming a sealed or closed iluid flow system within the pumps.

Yet fanother object of this invention is to vary the output of the secondjpump'in accordance with the 'amount of torque desired tto v-be applied to the driven shaft.

A still further object vof 'this invention is to supply a pair of pumping units connected together inlet to outlet, and outlet to inlet, with means for varying the ratio by varying the volume of output per revolution of the pumps inversely.

Another object of this invention is to utilize a speed-responsive governor for controlling an auxiliary pump, the speed-responsive governor being actuated by the power input shaft and also actuating the auxiliary pump by means-of the same shaft, whereby through intermediate means the auxiliary pump and speed-responsive governor operate on a "valve 'for controlling the `flow of fluid from `the auxiliarypump to vary thecomposite output torque of the two pumps which form the seale'dhydraulic system.

A still further object of this invention is to provide an extremely simplied mechanical device for `performing the above mentioned functions as well as numerousancillary functions.

'Other objects .and 'features `of novel-ty will become apparent to those skilled in the art, in following the description of the preferred form of the invention, .illustrated in Athe accompanying drawings, wherein:

sFigure x1 isaa longitudinal sectional vvie'w of the preferred form of the invention;

Figure -2is afvplan view-.of the invention shown infFigure 1;

y.Figure 3ds-a sectional view showingthe juxtaposed vpumps forming -a major portion of the inventionfand the control means therefor;

Figure`4 is a Yschematic view showing the auxiliary Apump and associated mechanism Afor controlling the torque outputof 'the two juxtaposed Pumps;

Figure 5 is a vvtransverse `sec-tional -view of the invention-shown in Figure .1

Figure 6 is aperspective view'of one of the plates forming a portion of the invention;

Figure 7 is `a side view Aof -a support 'for the ratiovarying angular plates;

:Figure '8 is fa perspective view "of one of the pistons in the j uxtaposed-pumps;

'Figure 9 is an yelevat-ionalview yof a bearing block yforming .a portion of each Vof the pumps and connectingthe same Figure 10 'isasectional detail oficonstruction takenonline l--Hl-of-Figure Scand inthe directionr of the arrows;

yFigure 11 isa sectional view taken substantially on the line l I-'I'| of Figure 1 land inthe direction'of the arrows;

Figure 12 is an elevational end view'ofone of thepumpelements;

Figure -13' is a -sectional view" taken on the line l--W of-Flgure -12 and in the "direction of the arrows;

Figure 14 is an elevational view vo 4anothrr pumpfcomponent;

Figure -15 is asectional'view taken `substantially on the lineflE-*IB Aof Figure '1'4"and`inth'e direction'of the arrows;

Figure 16 is a sectional view taken substantially onthe line I6-"f6 of "Figure'l 'andinthe direction of thefarrows; and

Figure 1'7 is fa lsectional viewtaken substantially on theline |"l-I1 ofFigure 16'an'd inthe direction `of the'an'ows.

This invention has been developed 4to provide a device for more l'eiiiciently 'and Ysmoothly transmitting va mechanical movement. For 'the best understanding of 'theinventiony itis deemed advisable to rst 'set Vforth the "operation thereof, which is as follows:

`Operation A lcomplete lcycle o'f operation, from a neutral totop'speed aznd'back to the neutral position includes'tne application of 'a torque tothe power or drive 'shaft lllwvhichiis vjolnfnalel'l vin a Ibearing l 2,

which is in turn associated with a frame or support generally indicated at I4. Under such conditions, the shaft I rotates and applies the same torque to a differential generally indicated at I6. Assuming the power take-off or driven shaft I8 to be stopped, the torque is transmitted wholly to the counter shaft 20. This counter shaft, of course, is thereby rotated, thereby, in turn, rotating a pump shaft 22.

A speed-responsive and/or manually operative control system (see Fig. 4) is also actuated by the counter shaft through the medium of intermediate gearing. The servomotor generally indicated at 26 is influenced upon predetermined conditions which will be described subsequently. However, it is noted that this servomotor actuates a rod 28.

When the drive shaft I8 rotates at a selected R. P. M., the driven shaft I8 will not be influenced when a pair of pumps (see Fig. 3) are in the neutral position. It will be noted that two pump assemblies are seen in Figure 3 having the inlet of one connected to the outlet of the other, and the outlet of the other connected to the inlet of the said one. By this means, a closed fluid system is supplied. It is seen that each pump must operate with an equal capacity, although the volume of each pump unit is readily adjustable by the control system seen in Figure 4. Thus, by manipulation of the rod 28, it is possible to obtain a Setting of the two pumps (first and second) so that no fluid is pumped when it is revolved. Thus, if no fluid is pumped, the second pump cannot be revolved: thereby, through the medium of gearing, one of the gears of the differential I6 is locked and the torque applied to the drive shaft IIJ is transferred to harmless rotation of the pump elements.

When increased torque or greater R. P. M. is applied to the shaft IU, the speed-responsive governor will move the hydraulic valve seen clearly in Figure 4, so that the fluid produced by the auxiliary gear pump also seen in this figure will flow to a servomotor and exert a force to move the rod 28 and thus change the front pumps angle plate and cause that front pump to produce movement of the fluid in the said sealed system.

The rear pump begins to revolve as soon as the ilrst pump has a place to pump its fluid and thus the action of the front pump, pumping fluid to the inlet of the rear pump, and the rear pump pumping fluid to the inlet of the front pump is set up. Simultaneously, the gear which was previously described as locked in the differential begins to revolve, thereby driving the rear pump and the driven mechanism including the driven shaft I8'.

Therefore, it can be seen that the power is transmitted through both direct gearing and the hydraulic transmitting mechanism. This double action occurs at all ratios of speed input to one of the double pumps to speed output of the other double pump` except at maximum R. P. M. and during a speed which might be considered neutral (wherein there is no rotation of the shaft I8). Also, this occurs when all power is transmitted by the differential directly to the shaft' I8 or when no power whatsoever is transmitted to the shaft I8.

I'he variance in ratio is controlled by the hydraulic transmitting mechanism, with the control system automatically selecting the proper ratio for that hydraulic transmitting mechanlsm to set up between the engine (drive shaft I8) and driven shaft I8. This ratio is varied and/or maintained by varying the proportion of the fluid pumped per revolution by one pump in relation to the fluid pumped per revolution of the second pump. As the capacity of the pumps must remain equal, this means that if the rear pump produces, for example, one cubic inch of fluid every revolution, it must revolve ten times as the front pump produces ten cubic inches of fluid per revolution. Thus, there is a ratio of ten to one. The control system may vary this ratio change an extremely small amount or completely, such ratio change being carried through the differential and to the driven member I8.

The ratio is changed by the control system, which, to increase the load on the shaft I0 and thus slow the shaft IIJ, decreases the mechanical advantage of the engine or the like which is driving the shaft I0 (over the driven member I8) by increasing the amount of fluid pumped by the first pump and decreasing the amount of fluid pumped by the second pump. Upon acceleration, the ratio is gradually changed to meet the changing ratio requirements, with the fluid pumped by f the first pump per unit revolution increasing and the fluid pumped by the pump of the rear unit decreasing as higher speed is attained.

At top speed, the transmission reverts the opposite of the neutral position. That is, the amount of fluid pumped by the rear unit has been decreased until no pumping action occurs. This locks the front pump and consequently the forward gear of the differential I6. All power is then transmitted from the drive shaft I0 through the medium of a partially locked differential to the driven shaft I8. Further acceleration of the shaft I0 will be transmitted directly to the shaft I8 as the hydraulic portion of the device is inoperative. If additional load is imposed upon the shaft I8 at any time to slow the shaft I8 below the selected R. P. M., then the governor will move the control valve in such a way as to influence the control system to increase the output of the rear pump and decrease the output of the front pump. Thus, the additional mechanical advantage mentioned above is utilized for actuation of the driven shaft I8 which will incidentally save wear on the prime mover which is actuating the shaft I0. The lightening of the load of the engine is reponsible for such a saving.

When the shaft iii is reduced insofar as speed is concerned, the control system will attempt to decrease the mechanical advantage of the driven member I8 to allow the engine or other prime mover which is associated with the shaft I0 to turn at the incident R. P. M. This action decreases the advantage of the driven member sufliciently to allow that member to force the engine or other prime mover to revolve at the selected R. P. M. as long as the driven member continues to be motivated.

When the driven member comes to a stop, the control system `will have moved the angle plate of the rear pump to its greatest angle, and the angle plate associated with the other pump to its smallest angle. Thus, the transmission is again in neutral and the driven member is locked with the power input shaft I0 free to rotate.

In performance of the above described operation, the structure necessary and desired incorporates many various conventional elements which are connected together in the following manner.

Frame construction The said frame generally indicated at I4 is supplied mostly for convenience and may include various elements. Among these elements is la housing 30 4which may partially or entirely encompass the operating'elements ofthe invention. 'I'he said shaft I0 is supplied in a suitable aperture adjacent the lower fportion of the housing 30 and is journaled in a bearing I2, vas described above. This bearing is vconnected with substantially parallel support members 32 and 34, respectively, which form the actual foundation or support.

This foundation or lsupport is substantially rectangular in configuration and has tie members '.36 extending thereacross for additional rigidity. The specific structure of the frame I4 is not of major importance, the frame'construction being ,made to yaccomodate the various elements of -the device in order that it may operate in the desired manner.

Dierential system The said power inputvr-r drive shaft I is supplied with a gear Stat one end thereof (see Figs. 16 and 17), which isenmeshed with a gear 40. Thisgear 40forms a portion ofa differential and journals a pair of spider gears 42 and 44, respectively, in suitable apertures therein. The said spider gears 42 and i4 maybe supplied with conventional pins or stub .shafts 46 and V48, respectively, which are journaledin bearings 50 and 52, asis seen .inFigure 17. The opposite ends of the saidpins 46 and 48 are journaled in a'central body .member 5`4 which, in turn, has opposed shafts .'56 ,and 58, respectively, associated therewith. These opposed shafts .are aligned and are received in recesses ends of the counter shaft 20 and the driven shaft I`8. y

An anti-friction bearing construction, preferably of the ro'ller type, may be supplied adjacent the terminal of the said aligned shafts and 58 and maybe seen at 60. It will be noted at -this point that any type of anti-friction bear1w ing may be supplied if it is found desirable7 and for simplicity and economy of structure, simple babbitt type bearings may be used.

Supplied on Vthe terminals of the said shafts I8 and 20 is a `pair of identical gears 62 and .64, respectively, which are constantly enmeshed with the said spidergears 42 and 44. As describedpreviously in the specification, the maintaining of the power take-olf shaft 'IB in a'locked position will permit rotation of the gear 64 and consequently the counter shaft`2`0 upon application of a torque to the shaft I0. However, the force taking the line of least resistance will apply the torquetothe shaft I8 in the event that itis more diflicult to rotate the counter shaft 20.

'Hydraulic transmission system Attention is now ydirected'primarily to 'Figures 3 1G :herein a pumping system is disclosed. In Figure 3, a central pump blockli is illustratedand thisblcck includesa pair-of chambers l0 andl';l respectively which are separated by means of .a partition T4. The block 68 is externally threaded in order to accommodate opposedidentical housings 16 and 18 respectively. Further, a plate 80 Ymay be attached to the said block 68 in order to support the block on the frameconstructicn by any suitable means such as bolting, riveting, welding or the like.

Upon further considerationof Figure 3, it will be seen that the pumping mechanism is symM metrical, there being identical vstructure on each side of a-transversecenter line. `Notingflrst the pump, which might be-considercdthe 'first pump, it is-quite apparent thata-cylinderblock 821s supplied with Aa flange M about the periphery `of one and thereof. This flange engages aplurality of bearings, preferably ofthe ball type 8B, which are interposed between the said flange 84 and the cage 78. By this expedient, the cylinder `block S2 bodily rotatable on the center block 68. l

`A ,plurality of pistons -88 having piston rods .9.0 rigidly secured thereto are reciprocablymounted in the cylinders of the said cylinder block.

Means for varying the stroke of the pistons 88 is provided, .and includes for the first pump an angle 'plate '.92 having-a plurality of radial grooves 94 therein. The ends of the piston rods 90 are engagedinthe grooves 84 whereby, upon rotation of the cylinder-block B2 with the angle plate 92 in aselected position, the stroke of the piston rods, and therefore the pistons, is regulated and directed in a prescribed course due to the radial slots 84.

'I'he plate 94 is attached to a backing member and `forms a part of the angle plate assembly. Thebacking member or angle plateassembly part 96 .is pivoted at'two places. Thebacking plate `includes Aan extension 91 and an extension 91. The extensions are slidable in bearings 98 and 98. The bearings are secured to the rod by means of a pivot pin |60, allowing swinging or pivotal movement of the bearings about the pivotpin |400 as an axis. The extensions are slidable through the bearings 98 and 08'. By this construction, rthe angle plate assembly is pivotally operable about its lower pin I0 as an axis in response to movement of the rod 28.

A central aperture is supplied in the backing plate 96 and is indicated at |02. I'his aperture has a continuation in the angle plate`92 as seen at |04'. Through this medium of the apertures, the shaft 22 is permitted to extend through the angleplate. The shaft is splined in a central aperture provided in the bearing block 82. In order to pivot'the backing plate 9'6, as previously described, the pin I I0 which is xed to the plate 96 is used, inasmuch as it is operable in the bearings |08, supplied in the frame.

A second pump, generally indicated at ||4, is of identical construction with respect to the rst pump. 'Ihis second pump includes pistons 88 having piston rods engageable in radial slots provided in the angle plate 92. The backing plate 96 which is identical to the backing plate 96 is supplied in` association with the angle plate.

The backing plate 96 has extensions which are operable in bearings 99and 99'. These bearings are fixed by means of the pivot |00 to the rod 28 in a manner identical to the attachment of the bearings 98 and 98. They also serve an identical function.

It is readily appreciated from an inspection of Figure 3 that upon manipulation of the rod 28, the stroke of the pistons 88' is regulated as is the stroke of the pistons 88. Moreover, since there is a sealed or closed hydraulic system connecting these pumps, the input of one pump necessarily reflects on the output of the other pump, hence the output torque of the shaft ||2. When the angle plates are in a selected position, the second pump I I4 transmits no torque, as the throw ofthe pistons of the first pump counterbalance the throw of the pistons of the second pump, thereby rendering torque outputa nullity.

In order to ll the chambers 'I2 and 10, respectively, a pair of filler plugs ||8 and |20 are supplied in apertures |22 and |24 and are held in place by any suitable means as vscrew threads. In order'to provide vends forl the cylinders within the cylinder blocks of each pump, plates |26 are supplied in each cylinder block with appropriate openings |28 therein in order to accommodate the piston rods 90 and form a passage therefor. Moreover, these plates |26 have keyways |30 in order to seat the pins which are either formed integral with the cylinder blocks or detachable in nature.

Control system For the control system, attention is directed primarily to Figure 4, wherein there is disclosed an arrangement of elements forming the major portion of the control system of the present invention. The counter shaft 20 has a bevel gear |30 rigidly attached thereto which is enmeshed with a complemental bevel gear |32. This lastmentioned bevel gear |32 is attached to a shaft |34 which, in turn, has a large gear |36 rigidly secured thereto. This large gear |36 is meshed with another gear |38 having a shaft |40 extending therefrom. It is now seen that upon rotation of the counter shaft 20, the gear |36 and the gear |38 will be rotated. Brackets |42 and |44, respectively, are attached to the said gear |38 and are rotatable therewith. Weighted members |46 and |48, respectively, are pivoted to the said brackets |42 and |44I and are so arranged as to be speed-responsive. Upon a relatively large speed, the weighted members tend to spread due to centrifugal force and thereby lift the shaft |4| which slides through the center of the gear |38. In accordance with a predetermined speed, the shaft |4| having a disk |50 at the top thereof is raised. Upon this raising, the spring |52 seated on the disk |50 is compressed against a stationary block or element |54. It is now seen that the raising or lifting of the shaft |4| is in response to the difference between the compressive force of the spring |50 and the centrifugal force motivating the Weighted members |46 and |48.

In order to effect substantially the same result, that is, to raise and lower the element |4|, a crank |56 is supplied on a pivot pin |58, which is anchored to the frame |4. An indicia bearing plate |60 may be supplied adjacent the crank |56 and a slot |62 is formed in one end of the crank |56. This slot has a pin |64 which rides therein, which pin in turn is attached to a suitable bracket |66. Of course, the said bracket |66 is associated with the movable portion of the block |54 in order to urge the same for transmission of force against the spring |52.

An auxiliary pump generally indicated at is supplied and the rotor |12 of the said pump is rigidly secured to the said shaft |34. It may now be seen that upon rotation of the shaft |34 not only does the gear |36 rotatable but also the rotor |12 is actuated.

A plenum chamber |14 is supplied in a suitable housing |16 and has a quantity of fluid stored therein. This quantity of fluid is permitted to circulate through the auxiliary pump |10 through the medium of a conduit |18. This conduit being received in the pump housing and the plenum chamber |14 receives the pumped fluid and conducts the same through a second conduit |80. This second conduit terminates in a valve body |82 and more specifically, in the valve chamber |84 thereof. A valve core |88 is rotatively received in the valve chamber |84 and is actuated by means of an arm |90 which is secured thereto. This arm |90 has a pitman |92 attached thereto in the usual manner for pitman rods and the opposite end of the said pitman is secured to a bellcrank |94. One arm of the bellcrank |94 has a slot |96 therein and a pin |98 rides freely in this slot. This last-mentioned pin |98 is an integral part or is secured 'rigidly to the said shaft |4|. The operation thus far described indicates a mechanism whereby, upon either manual or speed-responsive control, a valve may be regulated.

Communicated with the valve chamber |84 is a pipe |99 which terminates in the plenum chamber |14 for re-circulation of uid. Also communicated with the valve chamber is another conduit 200 terminating in the servomotor 26.

The preferable structure of the servomotor may be either diaphragm or piston type. For illustrative purposes, a cylinder housing 202 is supplied with a piston 204 therein. The said rod 28 is secured to the piston 202 and is actuatable therewith. The said conduit or pipe 200 terminates on one face of the piston while another conduit terminates in the valve chamber 84 and in the cylinder member 202, at the opposite face of the piston 204. On manipulation of the valve, it is readily apreciated that fluid may be supplied on either face of the piston head 204 in order to actuate the rod 28 in either of two directions.

Pressure responsive means is supplied in association with this system in order .to re-circulate a certain portion of the fiuid. This pressure-responsive means may be seen as obviously the cage 208 which has an adjustable and detachable plug 2|0 threadedly received in one end thereof.

A spring 2|2 or other suitable resilient biasing means is seated on the said plug 2|0 and reacts on a ball 2 4 or other suitable type of check valve. Communicated with the bore of the cage 208 is a small length of pipe 2|6 which intersects the conduit |80. Another small length of conduit 2|8 communicates the bore of the cage 208 with the plenum chamber |14.

Through the above described structure, the value of angularity of the angle plates 92 which are interposed on the supports 94 through the medium of the ball bearings 220 is effected.

In order to transmit torque from the counter shaft 20 to the pump shaft 22, the preferred means is the utility of a plurality of gears. For this structure, attention is directed primarily to Figure l wherein the gear 222 is shown as rigidly secured to one end of the counter shaft 20 and this 1astmentioned gear is enmeshed with a complemental gear 224 which is attached to the said shaft 22.

At the opposite end of the fluid transmission portion of the device, it is readily appreciated that the shaft ||2 terminates in a gear 226. In order to add the torque of the shaft 2|2 to the torque of the shaft I8 in the proper directions in order that they will not be opposing each other, an idler gear 228 is journaled on the frame I4 and this idler gear 228 engages another gear 230. Of course, the last-mentioned gear 230 is rigidly attached to the shaft I8, thereby rounding out the necessary structural elements appurtenant to the present invention.

It is apparent that many variations may be made without departing from the spirit of the invention such as the utility of a cover 230 for the said weighted members |46 and |48, and suitable bearing members 232 and 234 respectively in order to support the rod 28. These expedients and others may of course be resorted to without departing from the spirit of the invention. Accordingly, limitation is sought only in accordance with the scope of the following claims.

said first pump being connected with its inlet to the outlet of the second pump forming a closed fiuid flow system, said pumps including pistons which have piston rods, tiltable plates engaging the piston rods, said first pump having a shaft and said second pump having a shaft, means for controlling the angularity of said plates to regulate the speed of the shaft of the second pump relative to the speed of the shaft of the first pump, a driven shaft operatively s connected with said differential and the shaft of said second pump, means drivingly connecting the shaft of said first pump and said counter shaft, said plate controlling means including an auxiliary pump driven by said power input y shaft, a speed-responsive governor driven by said power input shaft, a valve actuated by said governor, said valve being communicated with said auxiliary pump, a rod secured to said plates, and

means secured to said rod and connected with said valve for motivating said rod.

2. The combination of claim 1 and said lastmentioned means including a servomotor.

3. A transmission comprising a frame having a drive shaft and a driven shaft, a counter shaft I" and a differential connecting said drive shaft, driven and counter shafts, a first pump having a shaft and an inlet and an outlet, a second pump having a shaft and an inlet and an outlet, both pumps carried by said frame, the inlet of the first pump being connected to the outlet of the second pump, and the outlet of the first pump being connected to the inlet of the second pump to form a sealed fluid system, means for selectively varying the amount of fluid pumped by the second pump with respect to the first pump during a single revolution of the pumps, means for drivingly connecting said counter shaft and the shaft of said second pump, means for drivngly connecting the shaft of said first pump and said drive shaft, said pumps having pistons with piston rods, said means for varying the amount of fluid pumped including a pair of pivoted plates engaging the piston rods, and a rod connecting said plates together with means for actuating said rod whereby said plates are operated simull0 taneously, said rod actuation means comprising an auxiliary pump, a plenum chamber connected with the auxiliary pump, a valve controlling the flow of fluid from said plenum chamber, a servomotor actuating said rod, and conduits connecting said valve and said servomotor.

4. A transmission comprising a frame having a drive shaft and a driven shaft, a counter shaft and a differential connecting said drive shaft, driven and counter shafts, a first pump having a shaft and an inlet and an outlet, a second pump having a. shaft and an inlet and an outlet, both pumps being carried by said frame, the inlet of the first pump being connected to the f, outlet of the second pump, and the outlet of the first pump being connected to the inlet of the second pump to form a sealed fluid system, means for selectively varying the amount of fluid pumped by the second pump with respect to the first pump during a single revolution of the pumps, means for drivingly connecting said counter shaft and the shaft of said second pump, means for drivingly connecting the shaft of said first pump and said drive shaft, said pumps having pistons with piston rods, said means for varying the amount of fiuid pumped including a pair of pivoted plates engaging the piston rods, a rod connecting said plates, means connected to said rod for actuating said rod whereby said plates are pivotally operated simultaneously, said rod actuation means comprising an auxiliary pump, a plenum chamber connected with the auxiliary pump, a valve controlling the flow of fluid from said plenum chamber, a servomotor actuating said rod, conduits connecting said valve and said servomotor, and a pressure-responsive check valve operatively connected with said valve and said plenum chamber.

5. The combination of claim 4 and a speed- I responsive device driven by said drive shaft and operatively connected with said first-mentioned valve to regulate said first-mentioned valve.

GILES P. LAY.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES FA'I'ENTS Number Name Date 1,077,454 Cooke Nov. 4, 1913 1,924,017 Bedford Aug. 22, 1933 2,485,126 Wood Oct. 18, 1949 FOREIGN PATENTS Number Country Date 218,889 Great Britain July 17, 1924 

